I used a ball for almost a year, and my opinion is that it's no better than a chair overall, and in some ways worse. Items 1, 2, 4, 5, and 7 in the list linked

I used a ball for almost a year, and my opinion is that it's no better than a chair overall, and in some ways worse. Items 1, 2, 4, 5, and 7 in the list linked above are completely untrue in my experience. Not only is it every bit as possible to sit with poor posture on a ball as it is in a chair, but the ball actually encourages poor posture in some circumstances. I found that as the day progressed and I grew tired, I settled into a low-energy perch with my feet wide, my butt hanging more rearward on the ball, and my back rounded. This is a very stable position on a ball -- no core correction needed. It's pretty much the worst posture possible, and it was extremely difficult to mindfully avoid it. When I get tired in a chair, I lean against the back, and if it's a good chair I won't be stressin out my discs.